Clouding composition for enamels and process of making



, A greater covering enanieling industry. can

of Halberstadt a. 11.,

ASSIGNOR, BY MESNE ASSIGNMENTS, TO

THE CHEMICAL FOUNDATION, INC., A CORPORATION OF DELAWARE.

CLOUDIN G COMPOSITION FOR ENAMELS AND PROCESS OF MAKING.

No Drawing.

To all whom it may concern:

Be it known that I. Pmmrr Eran, a subjcct of the German Emperor, andresident Germany, have invented certain new and useful Improvements inClouding Composition for Enamels and Processes of Making, of which thefollowing is a specification;

This invention relates to the clouding of enamels and other vitreousware and comositions therefor, and comprises particuarly such enamelsand compositions containing zirconium borate and zirconium oxid,preferably associated with an alkali fluorid compound, and processes ofmaking such enamels and compositions.

The use of zirconium oxid and other zirconium compounds for producingclouding in enamels is known, but zirconium oxid has the drawback thatit does not produce a uniform clouding and for that reason oftenproduces spotted enamels. Another drawback is that enamels produced withzirconium oxid, are liable to become dull or tarnished during firing.The last named fault is a chief characteristic of tin oxid substitutesmade from zirconium oxid.

Zirconium borate has been suggested as a specially suitable zirconiumclouding substance. According to the experience of the applicant, itpossesses, in fact this advantage over other-preparations, that theenamels are not so easily liable to become spotted and dull, but on theother hand, it has a comparatively very insignificant covering capacity.

It has been found that a zirconium borate strongly supersaturated withzirconium oxid such as, for instance, a product of the composition Zr().2B .,+elZr(.) has a much capacity than ordinary zirconium borate, andat the same time does not cause the enamels to become spotted and dull.Moreover it has been found advisable in the manufacture of thepreparation. to melt at the same time cryolite or a similar alkalifluorid salt. as this increases the covermg capacity of thesupersaturated zirconium borate.

It is true that it is known that cryolite, which is generally used as aflux m the at the same time exercise a ccrtainelouding action. Never-Specification of Letters Patent.

Patented Sept. 2, 1919.

Application filed November 6, 1916. Serial No. 129,830.

theless it was impossible to foresee that the clouding capacity of thesupersaturated borate repared according to this invention, would beimproved by cryolite being melted with it at the same time.

It has been found further that cheap raw zirconia can be used for themanufacture of the preparation, provided that a certain quantity of anoxidizing substance, preferably sodium nitrate, is added. Thisunexpectedly produces from the cinnamon brown zirconia a brightzirconium borate which during the enamelino produces an irr proachablewhite ClOllC ing.

Emam-plc. 70 parts of raw zirconia, 30 parts boracic acid, 20 partscryolite and 50 parts sodium nitrate are thoroughly mixed together, themixture is fused and, after cooling, ground very fine. The preparationthus obtained is an excellent whlte clouding medium.

I claim:

1. A process of clouding enamels and the like which comprisesincorporating in the enamel a composition containing zirconium and boronin combination with oxygen, the ratio of zirconium to boron beingsubstantially greater than that existing in zirconium borate (ZrO,.2B,O

2. A. clouding composition for enamels and the like comprising zirconiumand boron in combination with oxygen, the ratio of zirconium to boronbeing substantially reater than that existing in zirconium Eorate(ZrO,.2B O

3. A clouding composition for enamels and the like comprising zirconiumborate supersaturated with zirconium oxid.

4. A clouding composition for enamels and the likev comprising zirconiumzirconium oxid and an alkali fluorid compound. there being a pluralityof molecules of zirconium oxid for each molecule of zirconium borate.

5. A clouding composition for enamels and the like containing boron andzirconium in combination and obtainable by fusing together about 7 partsof zirconium oxid, 3 parts of boracic acid. some cryolite and sodiumnitrate, and finely dividing the cooled mass.

(l. A process of nmking a clouding composition for enamels and the likewhich together zirconium. oxid and boracic mad, the amount; of zirconium'oxid being substantially larger than that required to, form zirconiumborate (zrO fiBO 7 A process of a clouding comosition' for enamels andthelike which comprises fusing comprises fusing together analkalifiuorid compound, zirconium 02nd and boracic acid,

the amount of zirconium oxidbeing substan- 7 than thatrequired to form zrtially larger (ZrO .2B 'O coniumborat 8. A- process of, making aposition for enamels and the like which comprises fusing together rawzircoma, boracic acid and an oxidizing agent, the amount ofsubstantially larger 7 than zirconia being clouding com- Witnesses: I

that required to form zirconium borate PHILIP? EYE'R,

HENRY HASPER, v ALLEN F. JENNINGS,

acid, about

